1978 W116 MPH/RPM Transmission Question

[marken]

Hello,
I am a MB newby. I recently bought a 1978 280SE automatic. When taking off it starts out in gear and switches at about 15mph or so and then again I think about 30-40mph. When doing 40mph the tach reads 2500 RPM. When going 50mph it reads 3000 RPM. When going 60mph it reads 3500 RPM. I have read some things that say the transmission could be designed to start in 2nd thus it does go through four gears. Do these mph to RPM ratios sound normal or I am possibly not shifting into 4th. Any help would be appreciated. Thanks!!!


Kevin